Disaccharides that are reducing in nature are:

Options

A. sucrose and lactose
B. sucrose and maltose
C. lactose and maltose
D. sucrose, lactose and maltose

Answer

To determine which disaccharides are reducing in nature, we need to analyze the structures of the given disaccharides: sucrose, lactose, and maltose.

### Step-by-Step Solution:

1. **Understanding Reducing Sugars**:
- Reducing sugars are those that can act as reducing agents. They contain a free aldehyde or ketone group that can be oxidized, while they reduce another substance in the process.

2. **Analyzing Sucrose**:
- Sucrose is composed of glucose and fructose. The linkage between them is a glycosidic bond that involves the anomeric carbon of both sugars.
- In sucrose, both the anomeric carbons are involved in the glycosidic bond, meaning there is no free aldehyde or ketone group available.
- Therefore, sucrose is **not a reducing sugar**.

3. **Analyzing Maltose**:
- Maltose is made up of two glucose units. The structure of maltose has one of the glucose units with a free anomeric carbon (hemiacetal) because it is linked to the other glucose unit through the anomeric carbon of one glucose.
- This free anomeric carbon allows maltose to have a free aldehyde group, making it a **reducing sugar**.

4. **Analyzing Lactose**:
- Lactose consists of one glucose and one galactose unit. Similar to maltose, lactose has a free anomeric carbon on one of the units (either glucose or galactose).
- This free anomeric carbon allows lactose to also have a free aldehyde group, making it a **reducing sugar**.

### Conclusion:
- Among the disaccharides mentioned, **lactose and maltose** are reducing sugars, while **sucrose** is not.